An implantable medical device (IMD) is an apparatus that is typically placed inside a living body to monitor certain physiological signals and provide therapy to an organ or tissue. A typical IMD, such as a pacemaker, defibrillator or neurostimulator, is implanted subcutaneously in a convenient location beneath a patient's skin. Components of the IMD, such as electrical circuitry or batteries, are contained within a hermetically sealed housing. This housing is typically constructed to isolate IMD components from the human body. A typical IMD includes electrodes that are adapted to sense physiological conditions or to deliver therapy, for example the delivery of electrical energy to one or more portions of the heart of a patient. The IMD may include one or more electrical leads that couple one or more electrodes to electrical circuitry disposed within the IMD housing. An IMD may also include electrodes on the surface of the housing.
Leads are typically adapted to carry current from the IMD to the tissue to stimulate the tissue in one of several ways, again depending upon the particular therapy being delivered. Leads may also be used for sensing physiologic signals to determine when to deliver a therapeutic pulse to the tissue, and the nature of the pulse, e.g., a pacing pulse or a defibrillation shock. Alternatively, a catheter lead may be connected to an IMD to deliver drugs to various body parts for pain relief, defibrillation threshold reduction, and so forth.
Because IMDs are disposed within the human body, attention must be paid to interfaces between an IMD housing and leads or electrodes connected to IMD components disposed within the housing. These interfaces, also referred to as feed-through connectors, are typically constructed to ensure that the IMD functions properly and does not negatively interfere with bodily functions of a patient. For example, a feed-through connector may be adapted to prevent bodily fluids from entering a housing and interfering with the IMD components disposed within the housing. A feed-through connector may also isolate electrical currents carried by a lead or electrode from the IMD housing.
Many solutions have been proposed to connect electrical leads to an implantable medical device housing. For example, some feed-through connectors connect a lead to IMD components through an aperture formed in a portion of an exterior surface of the housing, such as disclosed in U.S. Pat. No. 4,678,868 to Kraska et al, U.S. Pat. No. 6,920,673 to Allen et al, and U.S. Pat. Pub. No. 2006/0247713 to Nicholson et al. These feed-through connectors typically extend perpendicularly outward from a portion of an exterior surface of the housing. These feed-through connectors also typically include an insulator that surrounds a portion of a lead in proximity to the housing in order to insulate the housing from the lead. Other IMD housings include a header or other hermetic extension of the housing to further isolate a feed-through connector, such as disclosed in U.S. Pat. Pub. No. 2008/0114413 to Fischbach et al. For IMD housings that include a header, a feed-through connection may be provided in a surface of the housing itself, or in a surface of the header. Still other IMD housings include a hermetic connector block extension that extends from an IMD housing header along a portion of the housing exterior, such as disclosed in U.S. Pat. No. 7,254,443 to Jelen et al.
Recently, elongated IMDs have recently been developed that are adapted to be implanted in the vasculature system of a patient instead of being implanted subcutaneously like conventional IMDs. These elongated intravascular implantable devices (IIDs) may take the form of a plurality of independent, substantially cylindrical or frustro-cylindrical housings, such as disclosed by U.S. Pat. No. 7,363,082 to Ransbury et al. These housings may be connected together through a series of flexible components such as bellows so that the elongated implantable medical device is flexible enough to be introduced to and disposed within the vasculature system of a patient.
Chronically implanting an IID within the vasculature system of a patient presents a number of problems that are significantly different than implanting a conventional subcutaneous IMD because the IID must be constantly exposed to the blood stream of a patient. In addition, the IID and leads or electrodes of an elongated IID must be sized, shaped, and arranged to be disposed entirely within the limited space and shape of an elongated vasculature organ, such as an artery or vein of the patient.
As such, existing feed-through connectors for IMDs are of limited for use with an elongated IID because typical IMD feed-through connectors are formed to protrude perpendicularly outward relative to an IMD housing surface or header. As a result, these IMD feed-through connectors are effectively limited only to the ends of a generally elongated cylindrical housing arrangement. If existing IMD feed-through connector were to be used at locations other than the ends of an IID housing arrangement, the feed-through connectors would present exposed protrusions that may interfere with blood flow within the vasculature organ or cause undesirable coagulation along one or more surfaces of the feed-through connector or housing. Therefore, a need exists for an improved isolation connector for an elongated intravascular implantable medical device.